Glow discharge and plasma systems are becoming every more present with the emphasis on renewable fuels, pollution prevention, clean water and more efficient processing methods. Glow discharge is also referred to as electro-plasma, plasma electrolysis and high temperature electrolysis. In liquid glow discharge systems a plasma sheath is formed around the cathode located within an electrolysis cell.
U.S. Pat. No. 6,228,266 discloses a water treatment apparatus using a plasma reactor and a method of water treatment. The apparatus includes a housing having a polluted water inlet and a polluted water outlet; a plurality of beads (e.g., nylon and other plastic type beads) filled into the interior of the housing; a pair of electrodes, one of the electrodes contacting with the bottom of the housing, another of the electrodes contacting an upper portion of the uppermost beads; and a pulse generator connected with the electrodes by a power cable for generating pulses. Some drawbacks of the '266 plasma reactor are the requirements of an extremely high voltage pulse generator (30 KW to 150 KW), a plurality of various beads in a web shape and operating the reactor full from top to bottom. Likewise, the plasma reactor is not designed for separating a gas from the bulk liquid, nor can it recover heat or generate hydrogen. In fact, the addition of air to the plasma reactor completely defeats the sole purpose of current research for generating hydrogen via electrolysis or plasma or a combination of both. If any hydrogen is generated within the plasma reactor, the addition of air will cause the hydrogen to react with oxygen and form water. Also, there is no mention of any means for generating heat by cooling the cathode. Likewise, there is no mention of cooking organics unto the beads, nor the ability to reboil and concentrate liquids (e.g., spent acids, black liquor, etc.), nor recovering caustic and sulfides from black liquor.
The following is a list of prior art similar to the '266 patent:
Patent No.Title481,979Apparatus for electrically purifying water501,732Method of an apparatus for purifying water3,798,784Process and apparatus for the treatment of moist materials4,265,747Disinfection and purification of fluids using focused laserradiation4,624,765Separation of dispersed liquid phase from continuous fluidphase5,019,268Method and apparatus for purifying waste water5,048,404High pulsed voltage systems for extending the shelf life ofpumpable food products5,326,530High pulsed voltage systems for extending the shelf life ofpumpable food products5,348,629Method and apparatus for electrolytic processing of materials5,368,724Apparatus for treating a confined liquid by means of a pulseelectrical discharge5,655,210Corona source for producing corona discharge and fluid wastetreatment with corona discharge5,746,984Exhaust system with emissions storage device and plasmareactor5,879,555Electrochemical treatment of materials6,007,681Apparatus and method for treating exhaust gas and pulsegenerator used therefor
Plasma arc torches are commonly used by fabricators, machine shops, welders and semi-conductor plants for cutting, gouging, welding, plasma spraying coatings and manufacturing wafers. The plasma torch is operated in one of two modes—transferred arc or non-transferred arc. The most common torch found in many welding shops in the transferred arc plasma torch. It is operated very similar to a DC welder in that a grounding clamp is attached to a workpiece. The operator, usually a welder, depresses a trigger on the plasma torch handle which forms a pilot arc between a centrally located cathode and an anode nozzle. When the operator brings the plasma torch pilot arc close to the workpiece the arc is transferred from the anode nozzle via the electrically conductive plasma to the workpiece. Hence the name transferred arc. The non-transferred arc plasma torch retains the arc within the torch. Quite simply the arc remains attached to the anode nozzle. This requires cooling the anode. Common non-transferred arc plasma torches have a heat rejection rate of 30%. In other words, 30% of the total torch power is rejected as heat.
A major drawback in using plasma torches is the cost of inert gases such as argon and hydrogen. There have been several attempts for forming the working or plasma gas within the torch itself by using rejected heat from the electrodes to generate steam from water. The objective is to increase the total efficiency of the torch as well as reduce plasma gas cost. However, there is not a single working example that can run continuous duty. For example, the Multiplaz torch (U.S. Pat. Nos. 6,087,616 and 6,156,994) is a small hand held torch that must be manually refilled with water. The Multiplaz torch is not a continuous use plasma torch.
Other prior art plasma torches are disclosed in the following patents.
Patent No.Title3,567,898Plasma cutting torch3,830,428Plasma torches4,311,897Plasma arc torch and nozzle assembly4,531,043Method of and apparatus for stabilization of low-temperatureplasma of an arc burner5,609,777Electric-arc plasma steam torch5,660,743Plasma arc torch having water injection nozzle assembly
U.S. Pat. No. 4,791,268 discloses “an arc plasma torch includes a moveable cathode and a fixed anode which are automatically separated by the buildup of gas pressure within the torch after a current flow is established between the cathode and the anode. The gas pressure draws a nontransferred pilot arc to produce a plasma jet. The torch is thus contact started, not through contact with an external workpiece, but through internal contact of the cathode and anode. Once the pilot arc is drawn, the torch may be used in the nontransferred mode, or the arc may be easily transferred to a workpiece. In a preferred embodiment, the cathode has a piston part which slidingly moves within a cylinder when sufficient gas pressure is supplied. In another embodiment, the torch is a hand-held unit and permits control of current and gas flow with a single control.”
Typically, and as disclosed in the '268 patent, plasma torch gas flow is set upstream of the torch with a pressure regulator and flow regulator. In addition to transferred arc and non-transferred arc, plasma arc torches can be defined by arc starting method. The high voltage method starts by using a high voltage to jump the arc from the centered cathode electrode to the shield nozzle. The blow-back arc starting method is similar to stick welding. For example, similar to a welder touching a grounded work-pieced then pulling back the electrode to form an arc, a blow-back torch uses the cutting gas to push the negative (−) cathode electrode away from the shield nozzle. Normally, in the blow-back torch a spring or compressed gas pushes the cathode towards the nozzle so that it resets to the start mode when not in operation.
The '268 plasma torch is a blow-back type torch that uses the contact starting method. Likewise, by depressing a button and/or trigger a current is allowed to flow through the torch and thus the torch is in a dead-short mode. Immediately thereafter, gas flowing within a blow-back contact starting torch pushes upon a piston to move the cathode away from the anode thus forming an arc. Voltage is set based upon the maximum distance the cathode can be pushed back from the anode. There are no means for controlling voltage. Likewise, this type of torch can only be operated in one mode—Plasma Arc. Backflowing material through the anode nozzle is not possible in the '268 plasma torch. Moreover, there is no disclosure of coupling this torch to a solid oxide glow discharge cell.
U.S. Pat. No. 4,463,245 discloses “A plasma torch (40) comprises a handle (41) having an upper end (41B) which houses the components forming a torch body (43). Body (33) incorporates a rod electrode (10) having an end which cooperates with an annular tip electrode (13) to form a spark gap. An ionizable fuel gas is fed to the spark gap via tube (44) within the handle (41), the gas from tube (44) flowing axially along rod electrode (10) and being diverted radially through apertures (16) so as to impinge upon and act as a coolant for a thin-walled portion (14) of the annular tip electrode (13). With this arrangement the heat generated by the electrical arc in the inter-electrode gap is substantially confined to the annular tip portion (13A) of electrode (13) which is both consumable and replaceable in that portion (13A) is secured by screw threads to the adjoining portion (13B) of electrode (13) and which is integral with the thin-walled portion (14).” Once again there is no disclosure of coupling this torch to a solid oxide glow discharge cell.
The following is a list of prior art teachings with respect to starting a torch and modes of operation.
Patent No.Title2,784,294Welding torch2,898,441Arc torch push starting2,923,809Arc cutting of metals3,004,189Combination automatic-starting electrical plasma torchand gas shutoff valve3,082,314Plasma arc torch3,131,288Electric arc torch3,242,305Plasma retract arc torch3,534,388Arc torch cutting process3,619,549Arc torch cutting process3,641,308Plasma arc torch having liquid laminar flow jet for arcconstriction3,787,247Water-scrubber cutting table3,833,787Plasma jet cutting torch having reduced noisegenerating characteristics4,203,022Method and apparatus for positioning a plasma arccutting torch4,463,245Plasma cutting and welding torches with improvednozzle electrode cooling4,567,346Arc-striking method for a welding or cutting torchand a torch adapted to carry out said method
High temperature steam electrolysis and glow discharge are two technologies that are currently being viewed as the future for the hydrogen economy. Likewise, coal gasification is being viewed as the technology of choice for reducing carbon, sulfur dioxide and mercury emissions from coal burning power plants. Renewables such as wind turbines, hydroelectric and biomass are being exploited in order to reduce global warming.
Water is one of our most valuable resources. Copious amounts of water are used in industrial processes with the end result of producing wastewater. Water treatment and wastewater treatment go hand in hand with the production of energy.
Therefore, a need exists for a plasma arc torch that can be operated in multiple modes.